#include <stdio.h>

int main() {
	int s,x;
	scanf("%d", &s);
	x=s/5; 
	switch(x)
	{
		case 20:
		case 19:
		case 18:
		case 17:printf("A");break;
		case 16:
		case 15:printf("B");break;
		case 14:
		case 13:printf("C");break;
		case 12:
		case 11:printf("D");break;
		default:printf("E");
	}
}
